Binding of bundles of newspapers, magazines, or like items presents special problems, which designers of binding machines, such as strapping machines, must address. Because such items often tend to be somewhat slippery in relation to one another, particularly if such items comprise glossy advertising inserts or similar materials, it often is a practical necessity to bind a bundle of such items by applying crossed polymeric or metal straps, round or flat wires, or other binding elements around the bundle. High conveying and binding speeds are mandated, in many instances, and spatial considerations are important.
Commonly, polymeric straps are used, as exemplified by oriented poly(ethylene terephthalate) or polypropylene straps, which may be heat-welded, joined with metal seals or joined otherwise at overlapped ends so as to form closed loops. Usually, such straps cross each other at right angles, along opposite faces of the bundle.
In prior machines for strapping loads of diverse types by applying crossed straps, three basic approaches are used, as explained below. If a load is strapped with two straps crossing each other at right angles, and with reference to a forward direction of the load, it is convenient to refer to one such strap as a longitudinal strap and to refer to the other strap as a transverse strap. A given load may have a plurality of longitudinal straps, a plurality of transverse straps, or both.
A first approach, as exemplified in Mertens U.S. Pat. No. 3,031,816, has been to apply the longitudinal and transverse straps around a load, in either order, at successive locations along a conveyor for the load. As exemplified in the Mertens patent, each longitudinal strap is pre-draped so as to extend vertically along a front face of a load. As a variation of the first approach, it is known to apply a first strap in a first strapping machine, to rotate the load by a quarter-turn, and to apply a second strap in a second strapping machine. Although it may be very useful in other applications, a strapping machine employing the first approach tends to be too long and too slow to be ordinarily used in strapping bundles of newspapers, magazines, or like items.
A second approach, as exemplified in Pasic U.S. Pat. No. 4,312,266, has been to apply a first strap around a load in a single strapping zone, to rotate the load by a quarter-turn, about a vertical axis, after the first strap has been applied, and to apply a second strap onto the load in the same strapping zone. Typically, complex mechanisms are used to rotate the load. Although it may be very useful in other applications, a strapping machine employing the second approach tends to be too slow to be ordinarily used in strapping bundles of newspapers, magazines, or like items.
Moreover, under the first or second approach, rotation of the load tends to disturb the load, particularly if the load comprises slippery items such as glossy advertising inserts for newspapers.
A third approach, as exemplified in Lang et al. U.S. No. 4,578,933, is to convey a load in a forward direction, into a strapping zone, with the load oriented in a particular way. The load is oriented with its vertical faces at angles of about 45.degree. relative to the forward direction. In the strapping zone, the longitudinal and transverse straps are applied onto the load, in either order. An advantage of the third approach is that strap guides and similar structures are positionable so as not to interfere with a load being conveyed into or from the strapping zone. A disadvantage of the third approach, however, is that the unstrapped load must be initially oriented with its vertical faces at the angles noted above. Thus, if the load is a bundle of newspapers, magazines, or like items, roation of the unstrapped bundle so as to orient its vertical faces at such angles can cause the newspapers or other items of the bundle to cascade, particularly if rotation is effected by mechanical means.
Any such approach requiring a bundle of newspapers, magazines, or like items to be somehow rotated before the bundle has been bound with crossed binding elements, such as straps is disfavored by many users because of their concerns over maintaining integrity of the bundle.
Hence, there has been a need, to which this invention is addressed, for a binding machine using a better approach to binding bundles of newspapers, magazines, or like items with crossed binding elements, such as straps.